1. Field of the Invention
The present invention relates to an electronic device that establishes a connection and communication state with an external electronic device via a data bus compliant with a predetermined communication format. The invention also relates to a method for updating authentication reference information when performing authentication processing by the above type of electronic device with an external electronic device.
2. Description of the Related Art
As digital data interfaces, IEEE1394 data interfaces are known. IEEE1394 data interfaces have a higher data transfer rate than, for example, small interface computer system interfaces (SCSI), and implements isochronous communication that ensures periodic transmission and reception of a required data size. Accordingly, IEEE1394 data interfaces are effective in transferring stream data, for example, AV (audio/video) stream data, in real time.
In view of the above-described background art, the following type of AV system has been proposed. Electronic devices, for example, various types of digital AV machines or personal computers, are connected with each other via a data bus compliant with prescribed data interface standards, for example, IEEE1394, so that AV data can be transmitted and received between the devices.
As the above-described AV system, the following type of system, a so-called “component AV system”, can be considered. An amplifier device is used as the main device, and various AV source output devices, for example, a compact disc (CD) player, a digital versatile disk (DVD) player, a video machine, are connected to the amplifier device via a data bus.
The amplifier device used in the above type of AV system serves the function of receiving AV source information transmitted from source devices via a data bus and of outputting the source information as an audio signal to a speaker. That is, the amplifier device has the function of selecting one of a plurality of source devices connected to a data bus (such a function is also referred to as an “input source selecting function”. This function is implemented by establishing a logical and mutual connection with a source device selected by the user.
Due to the developments of AV machines and data network systems, as described above, copying and transmission of digital data is becoming very easy, and thus, copyright protection for digital data content, for example, music and video, is becoming very important.
For conducting copyright protection for content data, various types of techniques, for example, data encryption, authentication between devices when connecting with each other, revocation of unsuitable devices in terms of copyright protection, have been proposed and put to practical use.
For example, Japanese Unexamined Patent Application Publication No. 11-259971 discloses a technique for conducting authentication for copyright protection.
When connecting devices by the above-described IEEE1394 interface, in particular, between devices for transmitting and receiving audio data or video data, data transmission is conducted after authenticating the devices with each other (for example, authenticating the devices as licensed devices provided with an authenticated copyright protection function).
For conducting the above authentication processing, predetermined information (hereinafter referred to as “authentication reference information”) is used. This authentication reference information is stored in each device, and it should be updated occasionally when authentication conditions are changed or so-called blacklist information indicating unsuitable devices is added.
Accordingly, each electronic device must update authentication reference information.
To allow each electronic device to effectively exhibit a copyright protection function, authentication reference information must be updated to the latest version as quickly as possible. It is thus preferable that the opportunity to input authentication reference information into each electronic device be increased. That is, by inputting authentication reference information in various input modes, the opportunity to update authentication reference information in each electronic device is increased.
However, due to a variety of input modes, update processing in a device may be confused when, for example, different types of authentication reference information are input into a plurality of paths, or older versions of authentication reference information may be input. Thus, if authentication reference information stored in a device is updated merely in response to the input of authentication reference information, update processing cannot be suitably performed.